IP mobility enables a mobile device to keep reachablity in the Internet using a home address (HoA), while moving from one network to another network. As a protocol implementing this IP mobility, the IETF (Internet Engineering Task Force) is currently configuring a standardization protocol called mobile IP. The mobile IP is a communication protocol having excellent performance and extensibility for mobility of a node in the Internet.
The mobile IP allows a node to change a connection point to the Internet without changing the IP address (home address), thus enabling the node to keep a connection to a transport layer or a higher-order layer while moving. Herein, the implementation of the node mobility does not require configuring a route specific to the host over the routing configuration of the Internet as a whole. For example, a typical scenario to be considered to use the mobile IP is in the wireless WAN (Wide Area Network) environment. In the wireless WAN environment, a mobile device may pass through a plurality of LANs (Local Area Network) having different addresses. The mobile IP may be used to give transparency when a communication device of a user in communication with the Internet moves between cellular base stations in the third-generation (3G) network. Currently, the mobile IP of IP version (IPv4) or of IP version (IPv6) is available.
Recently, support for local IP mobility is also being provided. The local IP mobility is IP mobility in a network topology (connection condition of a network) of a limited area. Even when the area of the network topology for the mobile node to move is limited, the actual geographical area may be relatively wide. This depends on mapping between the network topology and a radio communication area. As an executable scenario for local mobility, an example may include the arrangement of wireless LAN environment in a large-scale campus (e.g., university campus). A user located in the campus area can receive services such as e-mail, search, or Web-surfing while moving in the university campus. However, it is not said as good expansion that all WLAN access points in the campus area are accommodated in a single broadcast domain.
Due to some reasons (e.g., the link does not conform to IEEE802.3), a single VLAN (Virtual Local Area Network) cannot cover a part of the campus in some cases. In this case, it is desirable that the campus is divided into links of last-hop each provided by one more access routers. Thus, in order to have an invariant IP address usable in each area (the respective areas provided by the access routers) in the university campus, it is required to use a certain localized mobility management technique. NetLMM (Network-based Localized Mobility Management) is a working group in the IETF designing a protocol for network-based localized mobility. The following Non-Patent Document 1 introduces a localized mobility management protocol to conduct IP mobility management that is limited within an access network (or called a NetLMM domain). This protocol accommodates a change of the access network due to moving, thus localizing the moving.
When a mobile node connects with a NetLMM infrastructure, the mobile node first has to use a stateful address configuration processing or a stateless address configuration processing to configure an address with a LMA (Local Mobility Anchor) that is providing a service. Therefore, when the mobile node connects with a MAG (Mobile Access Gateway), the MAG sends, to the LMA, a location registration message including information of its own (ID) and an ID of the mobile node. The LMA responds to this message using a location registration confirmation message including a NetLMM prefix usable for router notification from the MAG to the mobile node. Then, the MAG sends a router notification (including the NetLMM prefix) to the mobile node connected therewith. When address configuration is completed, the MAG sends, to the LMA, a MN address setup message including the ID of the MAG, the ID of the MN, the address of the NetLMM, and the ID of a tunnel, thus registering the address of the mobile node at the LMA. The LMA creates a transfer state with respect of a packet to this message, and sends, to the MAG, a MN address reply message approving the packet setup. When receiving a MN address setup reply message indicating the approval, the MAG creates a transfer state concerning a packet addressed to the mobile node.
Recently, laptop and other hand-held electronic peripheral devices are being manufactured with a plurality of network interfaces. Meanwhile, as for mobile IPv6 (MIPv6) described in the following Non-Patent Document 2, a mobile node can associate a care-of address (CoA) of its own with a home address (HoA) at a home agent so that reachability can be realized even when the mobile node is away from a home network. Thus, for hand-held electronic peripheral equipment with several network interfaces, the mobile node can register a plurality of care-of addresses to a predetermined home address.
Currently the IETF working group for Mobile Nodes and Multiple Interfaces in IPv6 (Monami6) defines such a method of registering a plurality of care-of addresses. In order to identify a plurality of bindings for one HoA, the following Non-Patent Document 3 introduces an identification number called a binding unique identification number (BID). The BID is assigned to an interface or a CoA associated with one home address (HoA) of the mobile node. Thus, the HoA is associated with the mobile node, whereas the BID specifies each binding registered by the mobile node. The mobile node notifies the home agent of the BID by binding update (BU), and the home agent records the BID in a binding cache of its own.
Herein, assume that a mobile node having a plurality of interfaces tries to have simultaneous connection (or simultaneous association) with a single LMA in a NetLMM domain. Herein the simultaneous connection refers to the state where a node (multi mode node) having a plurality of interfaces connects with each of the plurality of interfaces simultaneously. When the mobile node having a plurality of interfaces connects with the same LMA via different MAGs using the ID of the MN, location registration messages sent from the MAGs to the LMA are nullified mutually (i.e., overwritten). Thereby, the LMA actually uses only one interface of the mobile mode in any case.
Herein, the following Patent Document 1 discloses a method of allowing a mobile node (mobile station) having a plurality of interfaces to use one global address at any one of the plurality of interfaces. The mobile station creates a link local IP address usable to local communication at any one of the plurality of interfaces. Then, the mobile station uses the link local IP address to obtain, from a global obtaining unit, one global address usable to global communication through all of the plurality of interfaces. Thus, there is no need for the mobile station to create a global address for each of the plurality of interfaces.
The following Patent Document 2 discloses a method of associating a plurality of link layer addresses with an IP address in a radio communication network. This method allows a client device to aggregate data links associated with the IP address, thus increasing the download capacity of data. This method further enables bi-casting of data to the client device from the IP address associated with the plurality of link layer addresses of a radio communication device. This method still further enables failure recovery when a communication link to a first link layer address becomes deteriorated by allowing downloading to a second link layer address.
Further, the NetLMM working group recently discusses adoption of a local mobility management protocol of another type. This protocol is called a proxy-mobile IP (PMIP: Proxy MIP), described by the following Non-Patent Document 4, for example.
The PMIP uses extended mobile IPv6 signaling as a signaling message between a MAG and a LMA. When a mobile node moves in a NetLMM domain, the mobile node presents an ID of the mobile node in an access approving processing, thus connecting with the MAG. The ID the MN is normally used to associate a policy profile of the mobile node that can be obtained from a local server.
The policy profile includes a feature of a network-base mobility service provided, parameters related (e.g., a prefix assigned to the mobile node, an address configuration mode permitted, and roaming policy), and parameters required to provide other network-base mobility services, for example.
When succeeding in access approval, the MAG obtains a policy profile of the mobile node from a local server. Thereby, the MAG can have all information required to execute mobility signaling related to the mobile node. Then, the MAG periodically sends, to the mobile node, a router advertisement (RA) message to make a notification of a prefix assigned to the mobile node.
When finding a prefix from the received RA message, the mobile node configures an IP address (e.g., a home address in a home domain, and a care-of address in an external domain) so as to conduct communication at an interface connected with the NetLMM domain. As long as the mobile node moves in the NetLMM domain, the interface connected with the NetLMM domain can always find the same prefix. This can be implemented by having each MAG connected with the mobile node to always obtain a profile of the mobile mode from the local server. Thus, the mobile node can always use the first configured IP address to conduct communication irrespective of the location in the NetLMM domain. As another method of configuring an address, a stateful address configuration method such as DHCP may be used to assign an address or a prefix to the mobile node.
As stated above, the LMA functions as a logical (topological) anchor point for each mobile node in the NetLMM domain. In order to function as the anchoring point for each mobile node, the LMA is required to update the current location of each mobile node. To this end, every time the mobile node connects with a MAG, the MAG sends, to the LMA, a proxy binding update (PBU) message. This PBU message binds a unique identifier of the mobile node to a care-of address (a unique identifier) of the MAG. This binding allows the LMA to send a packet to the mobile node via an appropriate MAG.
A mobile node having a plurality of interfaces that is located in a NetLMM domain does not always mean that all of the interfaces have to connect with the NetLMM domain. For instance, assume that the mobile node has a cellular interface and a WLAN interface, and a user of the mobile node makes a contract (usage contract) with a service provider for cellular services. Meanwhile, assume that the service provider has a WLAN access point in the NetLMM domain, and provides WLAN services as well. In this case, depending on the contents of the usage contract, the WLAN interface of the mobile node may not be permitted to access the WLAN access point of the service provider even during moving in the NetLMM domain.
The following Non-Patent Document 3 discloses a typical exemplary method of controlling access of a mobile node having a plurality of interfaces. The conventional technique disclosed in Non-Patent Document 3 specifies an interface of the mobile node using a unique identifier (e.g., media access control (MAC) address). Information such as a unique identifier of an interface used for connection, for example, is stored in an access control list existing in a network.
In the case where an interface of the mobile node tries to connect with the network via a switch, the switch uses the access control list to judge whether the mobile node has already connected with the network via another interface or not. If the mobile node has already connected with the network via another interface, the switch uses a policy related to the mobile node to confirm whether it is possible or not for the mobile node to conduct simultaneous connection with the network. If it is judged that the mobile node is incapable of conducting simultaneous connection based on the policy, the switch refuses access of the mobile node to the second interface.    Patent Document 1: United States Patent Application Publication No. 2005/0271032    Patent Document 2: United States Patent Application Publication No. 2004/0100922    Patent Document 3: U.S. Pat. No. 7,236,470    Non-Patent Document 1: G. Giaretta, K. Leung, M. Liebsch, P. Roberts, K. Nishida, H. Yokota, M. Parthasarathy and H. Levkowetz, “The NetLMM Protocol”, NetLMM Working Group Internet-Draft, Internet-Draft, draft-giaretta-netImm-dt-protocol-02.txt, Oct. 5, 2006.    Non-Patent Document 2: D. Johnson, C. Perkins and J. Arkko, “Mobility Support in IPv6”, Internet Engineering Task Force Request For Comments 3775, June 2004.    Non-Patent Document 3: R. Wakikawa, T. Ernst and K. Nagami, “Multiple Care-of Addresses Registration”, Monami6 Working Group Internet-Draft, draft-ieff-monami6-multiplecoa-00.txt, Jun. 12, 2006.    Non-Patent Document 4: S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury and B. Patil, “Proxy Mobile IPv6”, Internet Engineering Task Force Internet Draft: draft-ieff-netImm-proxymip6-00.txt, Apr. 8, 2007.
According to the technique disclosed in Patent Document 1, another interface of a mobile station (an interface different from the interface that creates the link local IP address) is not required to create a link local IP address and can use a global address for global communication immediately. However, there is a problem that there is a limit for the mobile station to use only one of the plurality of interfaces at a time. The technique disclosed in Patent Document 2 does not describe a method of associating a plurality of link layer addresses with an IP address in detail.